AudioPrism Quiet Line Noise Filters and Noise Sniffer

by Doug Blackburn

Filtering

Don’t have the budget for a big $500+ power-line conditioner for your audio system? How about something that works pretty well for $200? The minuscule Audio Prism Quiet Line[TM] Noise Filters ($200 for a box of eight) fill the bill quite handily. These little wall warts without cords will plug into any electrical outlet and provide effective filtering of nearby noise sources via parallel filtering elements (i.e., capacitance). AudioPrism outlines a strategy for placing the Quiet Line Noise Filters that involves, first of all, placing two to four Filters in electrical outlets in and near your system. The goal is to create a "quiet zone" around the equipment. You might place one where the digital components are plugged in, one near the amp, one near the surround decoder, one near the preamp. Next, place the remaining Quiet Line Filters in electrical outlets near obvious noise sources -- light dimmers, refrigerator, fans/motors, washing machine, TVs, computers, video games, fluorescent light fixtures, etc.

The results aren’t quite as spectacular as those of one of the better large power-line conditioners, but you really get your money’s worth of noise reduction and protection for your system. You will hear the sound improve as you install more and more of the Quiet Line Filters. You will hear greater silence, and everything will seem a little more transparent and "floaty" without the extra background noise. You tend to want to listen to your system longer because it just seems more right. Some details you never noticed before will become audible with the lowered noise floor.

Thus you can improve the sound of your system in a cost-effective way with a box of Quiet Line Noise Filters. Large and expensive power-line conditioners can be more effective and more sonically desirable if selected carefully. However, in the real world, some budgets just aren’t going to accommodate $500+ accessories as well as they can those that cost $200. And for your $200 you get maybe 30% to 50% of the improvement you get from the big guys -- definitely worthwhile.

Sniffing

To quantify how effective the Filters are, I used another AudioPrism product, the Noise Sniffer. The Sniffer plugs into an electrical outlet and removes the AC line frequency, 60Hz in my case, converting whatever noise is left to an audible buzz that is played back through a speaker on the unit. The louder the buzz, the worse the noise. There is a volume control, but no other adjustments.

I brought the Noise Sniffer to the listening room and plugged it in to what I thought was a quiet resistive dimmer on a floor lamp. Imagine my surprise when the Noise Sniffer buzzed like a colony of Africanized honey bees at the opening of hunting season on humans. This lamp was not directly connected to the dedicated circuits for the audio equipment. However, it was so noisy that the Noise Sniffer detected a very small amount of noise it created at the PLCs for the audio equipment. Plugging in a single Quiet Line Noise Filter to the same group of outlets the floor lamp was connected to almost completely silenced the Noise Sniffer, even removing the very slight residual noise at the PLCs for the audio equipment. It took just a single Quiet Line Noise Filter to knock down the noise from the dimmer in this floor lamp. Around the house, other dimmer switches could be silenced with properly placed Quiet Line Noise Filters. Little "fffffttttzzzz" or "click" noises passed to loudspeakers from amps or other audio components when the refrigerator or washing machine turn on or off were silenced as well. Ditto for the heating/cooling fan and floor/window fans. Fluorescent light fixtures? Noisy and silenced nicely by a Quiet Line.

I was pretty impressed with this performance, so I checked other audio components I had on hand with the Noise Sniffer and found a few that produced low levels of hum in the Noise Sniffer when the components were turned on. In every case a single Quiet Line Noise Filter in the same outlet silenced the Noise Sniffer. Taking the Noise Sniffer on field trips turned up some interesting results. Some amplifiers are pretty noisy. One particular powered subwoofer with a switching amplifier set a new record for how loudly the Noise Sniffer reacted. Keep in mind that the Noise Sniffer is not necessarily revealing RF/EMI noise. There are plenty of opportunities for noise at much lower frequencies, including noise down in the audio band caused by power-supply modulation.

The Noise Sniffer is quite interesting and could be something that more fanatical audiophiles might want. When taken on field trips, it never failed to ignite spirited conversations. I think dealers might find the Noise Sniffer a really interesting tool for improving knowledge about components that are noise sources. They could loan it to customers who can then analyze their homes and audio equipment for noise sources. Once customers realize they have noise sources in their homes, the addition of Quiet Line Filters or more expensive power-line-conditioning devices becomes a no-brainer. Dealers can also use the Noise Sniffer to improve the sound of demo systems by eliminating unexpected noise sources. Reviewers could benefit from having a tool like the Noise Sniffer around too.

If you’ve been reading what I’ve been writing about AC power, you know that I think power conditioning is indispensable. I used to think PLCs were toys for the guys with big budgets -- until I heard what effective power-line conditioning sounds like. I’ll never be without it again. You shouldn’t be either. If you need convincing, the Noise Sniffer is a great tool. If you are already convinced, the Quiet Line Noise Filters, at $200 for eight, are the least expensive way I know of to cut AC-power noise and improve the sound of your system.

...Doug Blackburn
db@soundstage.com

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